Ramps and heatbed getting too hot

I've just been attempting my first print and I've noticed that my heatbed heats up even when I haven't set it. It seems to just keep getting hotter and hotter and also behind the d8, d9 and d10 terminals on my ramps 1.4 board, it also gets very hot there.
Thanks
Ben

Ben,

Please let us know where you have the heated bed connected to the RAMPS board. Also, are you using an Arduino Mega?

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-David

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Check out my FolgerTech Prusa i3 (plexi) at MindRealm.net

Hi David, I have the heatbed in d8. And yes it's an arduino mega. I've noticed the metal component behind these terminals (unsure of the name) has left a burn on the underside of the ramps board around its solder points. Can this be fixed?
Thanks

D8 is the proper location. Your heated bed (or its wiring) may be shorted or otherwise faulty. Can you please disconnect the wires from D8 and measure the resistance of the wiring? The board can probably be repaired without much trouble. A photo of the wiring connection at the heated bed would be helpful as well...

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-David

Find me online at:
Thingiverse
Instructables.com
LinkedIn
Facebook

Check out my FolgerTech Prusa i3 (plexi) at MindRealm.net

Thanks for the reply. I currently don't have a multimeter available but I have noticed the back of the green terminal box is melted and the red led near this is always on.

Ben

I have the same issue, I measured the resistance of the wiring (the pair that comes out of the heatbed) it shows 0.0 Ohms, i tried to measure resistance fwhen connected to D8, it also measured 0.0 Ohms. Do you think the issue might be on the heathbed itself. I'll upload images when my phone is charged.

My heatbed keeps getting hot even after it reaches the Set Temperature (60C for PLA), it does not turn off when i send the off message to Bed. And it starts to heat as soon as a I plug the 12V Power.
Thermistor detects temperature correctly and it's set on T1

I'm using:
RAMPS 1.4 on top of an Arduino MEGA.
The RAMPS has a MOSFET (IRF3205)
The 3D printer model it's a Prusa i3

Carlos.

Check for shorts (power going to ground)
Remove heat bed and using the multimeter continuity setting, place the probes on the bed terminals you should get a beep.
Visually check the surface of PCB Are there any dips or pips in it's surface?

Mount the print bed upon the printer, hold one probe of the multimeter to a terminal and touch with the other around the print bed and any metal surface. If you get a beep that is where the short is.
If you have MDF-PCB heat-bed - Alu heat spreader. You might find that the Alu has poke into the PCB heat sink and causing a short.

Ensure that the pins and connections are tight.
Was it working fine before now?

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Supporting 3D Printers with Parts and Build services.
Printer: Ormerod 2 (528.4) Duel extruder set-up with Aluminium X-Rib, RRPro Firmware v1.11-ch (2016-04-08)

Thanks for the suggestions i'll try ASAP. The body of my Prusa i3 is Acrylic.

I'll unmount the heatbed and give it a check. I'll share you the details.

Edited 1 time(s). Last edit at 02/24/2016 08:26AM by deanvlue.

I've retested the heatbed with a multimeter, I was not measuring the resistance properly, I read on the Prusa i3 Wiki that the heat bed should display at least 1.2 Ohm, i got 2.0 so i guess the resistance is not the issue.

I also tested the way you told, checking for a short circuit within the Aluminum heatbed top, no shortchut there.

I'm attaching the Resistance measuring just for documentation sake:



I'll try test it again to watch how ir behaves.When i measure Voltage it displays 11.76V. should it be 12V?

I've checked again and the temperature keeps rising, i'll try to reset it with Pronterface, if that does not work i'll reupload the firmware just as a measure i'm not missing some configuration.

Edited 1 time(s). Last edit at 02/24/2016 11:31PM by deanvlue.

i've tried to set the:

#define BED_MAXTEMP 70

Max temperature to 70 in the firmware just to validate that at some point it should be turned off; temperature keesp rising and i'm getting this error in Pronterface console:

Error:Temperature heated bed switched off. MAXTEMP triggered !!
[ERROR] Error:Temperature heated bed switched off. MAXTEMP triggered !!

Errorrinter stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting)
[ERROR] Errorrinter stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting)

I'm guessing it's the MOSFET that is not working, can you give me some pointers on how to check it?

[SOLVED]

I went into the IRC channel, they told me that if the LED2 turns on immediately after connecting the issue might be the MOSFET, i bought a IRLB4132 which is common here in Mexico and that i investigated that it's similar to the ones recommended for the heatbed.

I removed the old MOSFET that goes into the heatbed by clipping it off ( their recommendation was that it would be easy to desolder, which it was) and then installing the new MOSFET.

Problem SOLVED! when i pulg in the boad the LED2 keeps OFF, and once i set Pronterface to heat it, the LEDs turn ON, once it reaches the MAX TEMP it turns off.

Hope this solution applies to everybody having this issue.

Thanks.